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Provides instructions on parse error caused by code scaffolding in learnr tutorial #153

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merged 11 commits into from Dec 8, 2020
Merged

Provides instructions on parse error caused by code scaffolding in learnr tutorial #153

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393482d
Provides instructions on parse error caused by code scaffolding in le…
gadenbuie Sep 28, 2020
23e490f
Update R/grade_learnr.R
schloerke Oct 27, 2020
2744f8f
Merge master branch and resolve conflicts
gadenbuie Dec 3, 2020
cccfb20
Refactor parse error handling
gadenbuie Dec 3, 2020
d56ec39
Update unparseable code message
gadenbuie Dec 4, 2020
5a8a4e4
Rename default exercise.parse.error grade_parse_error()
gadenbuie Dec 4, 2020
8ee092f
Use sQuote() instead of shQuote()
gadenbuie Dec 4, 2020
d64cb2d
Add notes about overwriting to_check_fn with parse error grader
gadenbuie Dec 4, 2020
8360237
Use paste0() instead of sQuote()
gadenbuie Dec 4, 2020
280ecb5
Add NEWS entry for grade_parse_error()
gadenbuie Dec 4, 2020
6b01ceb
white space
schloerke Dec 7, 2020
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48 changes: 32 additions & 16 deletions R/grade_learnr.R
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Expand Up @@ -85,22 +85,7 @@ grade_learnr_ <- function(label = NULL,
user_code <- tryCatch(
parse(text = user_code %||% ""),
error = function(e) {
parse_checker <- getOption(
"exercise.parse.error",
function(...) {
graded(
correct = FALSE,
message = paste(
"Uh oh, the R code produced a syntax error:",
conditionMessage(e),
"\nCheck that you have closed every \", ', (, and { ",
"with a matching \", ', ), and }. Also look for missing ",
"commas. R cannot determine how to turn your text into ",
"a complete command."
)
)
}
)
parse_checker <- getOption("exercise.parse.error", grade_learnr_parse_error)
# check that parse_checker is a function with proper args
do.call(parse_checker, list(parse_error = e, learnr_args = learnr_args))
}
Expand Down Expand Up @@ -186,6 +171,37 @@ grade_learnr_ <- function(label = NULL,
)
}

grade_learnr_parse_error <- function(parse_error, learnr_args) {
# Code scaffolding in exercise code will cause parse errors, so first check
# for blanks. We consider a blank to be 3+ "_" characters.
n_blanks <- sum(vapply(
gregexpr("_{3,}", learnr_args$user_code),
function(x) sum(x > 0),
integer(1)
))
msg <- if (n_blanks > 0) {
paste0(
"The exercise contains ",
if (n_blanks == 1L) {
"1 blank"
} else {
paste(n_blanks, "blanks")
},
". Please replace the '____' with valid R code."
)
} else {
paste(
"Uh oh, the R code produced a syntax error:",
conditionMessage(parse_error),
"\nCheck that you have closed every \", ', (, and { ",
"with a matching \", ', ), and }. Also look for missing ",
"commas. R cannot determine how to turn your text into ",
"a complete command."
)
}
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graded(correct = FALSE, message = msg)
}


#' @rdname grade_learnr
#' @export
Expand Down
9 changes: 9 additions & 0 deletions tests/testthat/test_grade_learnr.R
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Expand Up @@ -83,6 +83,15 @@ test_that("Grade learnr check_code", {
expect_false(parse_error$correct)
expect_true(parse_error$type == "error")

# Code scaffolding produces informative parsing error message
one_blank <- grade_learnr(user_code = "____(mtcars, cyl)")
expect_false(one_blank$correct)
expect_true(grepl("1 blank", one_blank$message))

three_blanks <- grade_learnr(user_code = "________(___, ____)")
expect_false(three_blanks$correct)
expect_true(grepl("3 blanks", three_blanks$message))

# Can customize the feedback through an exercise.parse.error function
parse_error_func <- function(parse_error, learnr_args) {
graded(
Expand Down